JPH09144668A - Gear pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily pressurize a shaft seal part from the inside when a discharge fluid has a low pressure or high viscosity, and surely prevent the penetration of the atmospheric air in a self-lubricating gear pump by providing an inlet side circulating passage, and providing a pressure regulating means for shaft seal part thereon SOLUTION: A pressure regulating means A for a shaft seal part S is provided on an inlet side circulating passage 9. The passage diameter of the inlet side circulating passage is throttled by the pressure regulating means A, whereby the shaft seal part S is satisfactorily pressurized from the inside even when a discharge fluid has a low pressure or high viscosity, and the penetration of the atmospheric air can be surely prevented. Since the inlet side circulating passage 9 can be perfectly blocked by the pressure regulating means A, such a state can be eliminated that the air is penetrated through it in the maintenance work of the shaft seal part S to ruin a large quantity of material (supplying fluid) extending over a fluid tank, and the fluid can be effectively utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear pump which is preferably used for feeding and extruding high molecular weight polymers such as molten synthetic resins and high viscosity fluids such as chemicals.

[0002]

2. Description of the Related Art Conventionally, a self-lubricating gear pump has been used which lubricates a sliding portion such as a gear shaft of a drive gear or a driven gear and its bearing portion with a fluid which it carries. In self-lubricating gear pumps, the high pressure of the fluid sent on the discharge side is used to create a gap between the gear and the bearing, and a separate discharge side return passage that penetrates from the discharge port to the gear shaft. From
After the high-pressure fluid on the discharge port side is guided to the sliding portion and lubricated, it is returned to the suction port through a suction port side return passage extending from here to the suction port. Alternatively, when the liquid pressure on the discharge port side is too high to be used for reflux as it is, there is also devised a device provided with a discharge side reflux adjusting means for adjusting the reflux amount or the reflux pressure according to the pressure.

In such a conventional gear pump,
Since the drive shaft needs to be connected to a drive source such as a motor, it is necessary to project from the casing to the outside of the pump. To prevent the lubricating (liquid transfer) fluid from leaking through the penetrating part of the drive shaft, a mechanical A shaft sealing mechanism such as a seal, a gland packing, a labyrinth seal, etc. is selected and provided depending on the liquid type.

[0004]

By the way, in this type of gear pump, the suction port is used by connecting the suction port to the vacuum container in which the liquid sending fluid is sealed and the fluid surface pressure becomes vacuum, that is, the suction port side is a vacuum. It is often used in situations where In such a case, if the discharge pressure is low, the shaft seal part cannot be sufficiently pressurized from the inside, and the shaft seal part becomes a negative pressure, and the atmosphere enters the pump interior through the shaft seal part, causing When mixed with the product, air bubbles may form in the product, which may lead to deterioration in quality.

Further, since the diameter of the return hole is fixed, when the viscosity of the fluid to be sent changes greatly, the resistance in the return path changes greatly, and the shaft seal portion can be stably pressurized from the inside. It cannot be done, and the atmosphere invades and mixes with the fluid to be sent.

Further, since a liquid-feeding fluid such as molten plastic permeates the shaft sealing portion and is easily solidified when a mechanical frictional force is applied to the shaft sealing portion, the shaft sealing mechanism that handles this type of fluid is subject to severe wear and short-term. In the meantime, the sealing performance is reduced. In the conventional type, the sliding part of the shaft seal part is made up of consumable parts such as gland packing and shaft sleeve, and the shaft sealability is maintained by maintaining and exchanging this in a short period of time to improve product quality. Although it is guaranteed, every time maintenance or replacement of these shaft seals is performed, the atmosphere enters the vacuum or low-pressure pump suction port side through the recirculation path and enters not only the pump but also the fluid tank connected to the suction port. However, it is unavoidable that the air invades, the air bubbles are mixed in the liquid to be fed, and it becomes useless, and a large amount of fluid is wasted.

In view of such circumstances, the present invention can suppress the intrusion of air even when the shaft seal portion of the gear pump is replaced, and the shaft seal portion even when the discharge fluid has a low pressure or a high viscosity. It is an object of the present invention to provide a gear pump capable of reliably pressurizing the inside of the vehicle and reliably preventing the invasion of the atmosphere.

[0008]

In order to achieve the above object, a gear pump according to the present invention comprises a pump casing 1 provided with a suction port 4 and a discharge port 5 for a fluid to be fed, and in the casing 1. A gear pump that rotates a provided gear 7 by a drive shaft 6 extending from a casing 1 via a shaft sealing portion S to discharge a liquid-feeding fluid from a discharge port 5, and a part of the liquid-feeding fluid is a drive shaft. 6, which is used for lubrication between the bearing 6 and the bearing 8, is provided with an inlet-side return passage 9 for recirculating the bearing 6 from the drive shaft 6 to the inlet 4, and the pressure adjustment of the shaft seal portion S is performed in the inlet-side return passage 9. It is characterized in that means A is provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a gear pump according to the present invention will be described below with reference to the drawings.

The pump casing 1 has a cylindrical case body having an intake port 4 and a discharge port 5, a side plate 2 configured to cover the left side in the figure, and a stuffing box constituting a right wall. 3 and 3. The suction port 4 is connected to a vacuum container or the like in which an object to be liquid-fed such as molten plastic before molding is sealed, and the discharge port 5 is connected to a pipe or the like connected to a molding machine or the like at a later stage. Inside the casing 1, a drive shaft 6 that penetrates the stuffing box 3 is provided.
And a gear 7 fixed thereto, and a bearing 8 for supporting the drive shaft 6, are arranged, and the drive shaft 6 and the gear 7 are rotationally driven by a drive source such as a motor (not shown), so Is squeezed out from the suction port 4 to the discharge port 5. At the same time, by utilizing the high hydraulic pressure at the discharge port 5, the gear 7 and the bearing 8
Or a discharge port side recirculation path 10 which is separately provided so as to penetrate from the discharge port 5 to the drive shaft 6. (3) The inner pressure of the shaft sealing portion S is guided to a sliding portion such as a gap with the inner peripheral surface so as to be equal to or higher than atmospheric pressure. The arrows in the figure indicate the flow of the lubricating fluid.

If the liquid pressure of the liquid to be sent at the discharge port 5 is too high or the viscosity is low, the amount of reflux from the discharge port side return passage 10 becomes unnecessarily large, and the shaft seal portion S is over-pressurized. However, in order to prevent this,
The discharge-side reflux passage 10 is provided with discharge-side reflux adjusting means B capable of changing a part of the flow passage diameter. In the configuration shown in the figure, the hole diameter of the discharge-side reflux passage 10 is obtained by rotating the shaft. The tip portion moves in the direction of closing the valve, eliminating the above-mentioned inconveniences such as overpressurization and excessive reflux.

On the contrary, when the liquid pressure of the liquid to be delivered at the discharge port 5 is too low or the viscosity is high, the resistance in the discharge side return passage 10 which is a fine hole is large and the return amount and the liquid pressure are insufficient. The shaft seal portion S cannot be sufficiently pressurized from the inside, and the inside of the shaft seal portion S becomes a negative pressure so that the atmosphere tries to enter into the pump through the shaft seal portion S. However, the gear pump according to the present invention Then, as a characteristic configuration thereof, there is provided a suction side return passage 9 communicating from the drive shaft 6 to the intake port 4, and a part of the passage diameter is changed in the middle of the suction side return passage 9 so that the inside of the shaft seal portion S is changed. It is equipped with a pressure adjusting means A capable of increasing the pressure.

In the embodiment shown in the figure, the pressure adjusting means A is constructed such that a plunger having a gland packing around it moves in the direction in which the tip of the plunger closes the hole diameter of the suction side return passage 9 by the axial rotation of the adjusting valve. However, other than this, a publicly available configuration that allows the diameter of the flow path to be changed is applied.

When the hole diameter of the suction side return passage 9 is narrowed by the pressure adjusting means A, the flow rate escaping from the shaft sealing portion S to the suction port 4 is suppressed and the hydraulic pressure inside the shaft sealing portion S rises. As a result, even if the liquid pressure of the liquid to be delivered at the discharge port 5 is too low or the viscosity is high, the shaft seal portion S can be sufficiently pressurized from the inside, and the inside of the shaft seal portion S becomes a negative pressure. Atmosphere is shaft seal part S
The inconvenience of entering the inside of the pump through the is eliminated.

By the way, since a liquid-feeding fluid such as molten plastic permeates the shaft seal portion and is easily solidified when a mechanical friction force is applied to the shaft seal portion, the shaft seal portion S of a gear pump that handles this type of fluid is severely worn. , The sealing performance will be reduced in a short period of time. For this reason, the sliding portion of the shaft sealing portion S is constituted by consumable parts such as the gland packing S1 and the shaft sleeve S3, which directly slide as shown in the figure. It maintains the sealing ability and guarantees the quality of the product. When performing maintenance replacement of the shaft seal part S,
The suction side return passage 9 is completely closed by the pressure adjusting means A described above. In this way, air enters the suction port 4 side from the shaft portion that is released to the atmosphere through the recirculation passage 9 and the suction port 4
There is no possibility that the atmosphere will enter the fluid tank connected to the, the air bubbles will be mixed into the liquid-feeding fluid, it will become unusable, and a large amount of the fluid will be wasted.

[0016]

The self-lubricating gear pump according to the present invention is provided with the suction inlet side return passage 9 and the pressure adjusting means A of the shaft sealing portion S provided therein, whereby the discharge fluid has a low pressure and a high viscosity. Even in the case of, the shaft sealing portion S is satisfactorily pressed from the inside,
It is possible to reliably prevent the invasion of the atmosphere. Further, since the suction side return passage 9 can be completely closed by the pressure adjusting means A, during maintenance work of the shaft seal portion S, the atmosphere intrudes from here to reach the material tank. No waste of material (fluid sending fluid)
The material can be effectively used.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a self-lubricating gear pump according to the present invention.

[Explanation of symbols]

 A ... Pressure adjusting means B ... Discharge side reflux adjusting means S ... Shaft sealing part S1 ... Gland packing S2 ... Gland presser S3 ... Shaft sleeve 1 ... Pump casing 2 ... Side plate 3 ... Stuffing box 4 ... Suction port 5 ... Discharge port 6 … Drive shaft 7… Gear 8… Bearing 9… Suction port side return passage 10… Discharge port side return passage

Claims (1)

[Claims] 1. A pump casing provided with a suction port and a discharge port for a liquid feed fluid, wherein a gear provided in the casing is rotated by a drive shaft extending from the casing via a shaft sealing portion and is fed. A gear pump for discharging a liquid fluid from a discharge port, comprising a suction side return passage for returning a part of the liquid sending fluid from the drive shaft to a suction port after utilizing a part of the liquid sending fluid for lubrication of the drive shaft. A gear pump, wherein a pressure adjusting means of the shaft sealing portion is provided in the suction inlet side return passage.